1. Filed of the Invention
The present invention relates generally to the field of optical fibers, and particularly to dispersion managed optical fibers and methods of the making the fibers.
2. Technical Background
The recent advent of wavelength division multiplexing and amplifiers has increased system requirements to lower the dispersion and dispersion slope of the optical fiber. Several methods of making dispersion managed fiber have previously been disclosed that address these properties. See, for example, U.S. patent application Ser. No. 08/844,997 (Berkey et al.) filed Apr. 23, 1997, and U.S. patent application Ser. No. 08/584,868, filed Jan. 11, 1996, the specifications of which are all hereby incorporated by reference.
Many of the methods to date have been relatively complex and therefore may involve higher cost than more standard methods of manufacture because of this complexity. It would be desirable to develop an alternative, easier method to manufacture optical fiber whose dispersion characteristics vary between positive and negative along the longitudinal direction of the optical fiber, particularly in the 1550 nm operating window.
One aspect of the present invention is an optical fiber which includes a central core glass region with a first refractive index profile. The fiber also has a second core glass region adjacent to and surrounding said central region, said second region having a thickness that varies along an axial direction of said second region and having a second refractive index profile that differs from said first profile.
Another aspect of the invention is an optical fiber preform which includes a central core glass or soot region with a first refractive index profile. The fiber also has a second core glass region adjacent to and surrounding said central region, said second region having a thickness that varies along an axial direction of said second region and having a second refractive index profile that differs from said first profile.
A further aspect of the invention includes a method of making an optical fiber preform. This method includes inserting a rod of a material suitable for forming a glass region into a glass tube having a varying wall thickness along its axial or length direction. The material of the rod has a different refractive index profile than the material of the tube. The invention may also include a method of making an optical fiber.
A fiber produced in accordance with the invention includes the advantage of being a dispersion managed fiber. A fiber produced in accordance with the invention also has the advantage of being seed free. The method of producing a dispersion managed fiber in accordance with the invention is an easily industrializable process.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.